How to waterproof window sill from condensation damage?

[kyap]

With the days getting colder, one of our windows starts getting condensation overnight which pools down into the wooden windowsill. Last winter enough water seeped in that it caused the wood to expand and ruptured the paintwork. 

Is there an easy way to waterproof the windowsill to prevent more water ingress? Or alternatively a good way to prevent the amount of condensation build up?

I thought of just painting over the windowsill with a thick coating of exterior paint but that won't cover the gap between the window frame and windowsill.

 

[MitchellMc]

Hi @kyap,

To help waterproof the windowsill, I'd suggest using a paintable gap filler to seal the cracks between the window frame and sill first. Once that’s dry, apply two coats of a quality enamel paint over the entire sill. It's that painted enamel finish that provides the waterproof barrier and stops moisture from soaking into the timber.

As for preventing condensation, you could try cracking a window slightly overnight to let in some fresh air, though I completely understand that’s not ideal when you're trying to keep the room warm. Running a dehumidifier in the room would also help reduce the amount of moisture in the air and can be a really effective long-term fix. 

Please let me know if you have any questions.

Mitchell

[kyap]

Thanks MitchellMc as always for your helpful response!  Definitely sounds doable and good to learn about enamel paints. Will give it a try when I have spare time on a weekend.